XF86(4) BSD Programmer's Manual XF86(4)NAMExf86 - XFree86 aperture driver
SYNOPSIS
option APERTURE
DESCRIPTION
On alpha, amd64, cats, i386, macppc, and sparc64 the /dev/xf86 driver
provides access to the memory and I/O ports of a VGA board and to the PCI
configuration registers for use by the XFree86 X servers when running
with a kernel security level > 0.
The X servers require the use of this driver.
ACCESS CONTROL
Access to the /dev/xf86 device is allowed when the sysctl variable
machdep.allowaperture >= 1. This variable (which has a default value of
0) can only be manipulated when the security level is <= 0, so it should
be set in /etc/sysctl.conf. The possible values for machdep.allowaperture
are:
0 the aperture driver is disabled. Opening it returns EPERM.
1 the aperture driver allows access to standard VGA framebuffer and
BIOS. Access to pci(4) configuration registers is also allowed.
2 in addition to allowing access to pci(4) configuration registers,
the aperture driver allows access to the whole 1st megabyte of
physical memory, permitting use of the int10 emulation in XFree86
4.0.x. Note that this can cause some security problems, since the
process that has access to the aperture driver can also access
part of the kernel memory. This mode is not supported on alpha or
sparc64.
SEE ALSOXF86_Accel(1), XF86_SVGA(1), options(4), pci(4), sysctl.conf(5),
config(8), sysctl(8)HISTORY
/dev/xf86 was introduced as a loadable kernel module for NetBSD 0.9c with
XFree86 3.1. It was integrated as an in-kernel device on OpenBSD 2.3. It
is required in order to allow access to I/O ports for all X servers since
OpenBSD 2.4.
AUTHORS
The aperture driver was written by Matthieu Herrb.
BUGS
This driver allows access to all addresses above physmem. It should be
restricted to the actual address range of the video memory.
MirOS BSD #10-current February 20, 1998 1
